Potential Impact of Climate Change on Subsurface Drainage in Iowa's Subsurface Drained Landscapes

摘要

The study presents hydrologic simulations assessing the potential impact of climate change on subsurface drainage and its pattern in Iowa's subsurface drained landscapes. The contemporary (representing the decade of 1990s) and future (representing the decade of 2040s) climatic scenarios were generated by downscaling the projections of global climatic model HadCM through two regional climatic models RegCM2 and HIRHAM to a regional grid box of 52-55 km~2, which contains Perry, IA. These climatic scenarios were used to drive the field scale deterministic hydrologic model DRAINMOD to simulate subsurface drainage from one of Iowa's predominant hydric soils, WEBSter, cultivated with Continuous Corn (WEBS_CC), and equipped with a conventional drainage system (30-m drain spacing at 1.2-m drain depth). The simulation results consistently indicate an increase in subsurface drainage from WEBS_CC under future climatic scenario as compared to contemporary climatic scenario. This increase in subsurface drainage would be more in the winter months (from December to March) and early spring months (from April to May) than summer and fall months. Since subsurface drainage is a primary carrier of nitrate-nitrogen (NO_3-N) from the agricultural lands, the extrapolation of this study simulations suggest that there would be a potential for increased NO_3-N loss from Iowa's subsurface drained landscapes under future (in the decade of 2040s) climatic conditions.